If you have pain, weakness or numbness in your back, legs, neck, arms or hands, measuring the speed and degree of electrical activity in your muscles and nerves by way of electrodiagnostic testing can help your orthopedist make a proper diagnosis, says Dr. Syed S. Rahman in his recent blog.
When a patient comes into my office with pain, numbness or tingling in his/her legs or arms, I often will order an electrodiagnostic nerve test to diagnose abnormal nerve functions. As well as being a useful tool to diagnose abnormal nerve functions, electrodiagnostic nerve testing is also used to determine the exact location of a nerve injury, the severity of a nerve condition, and how well nerves are responding to treatments.
There are two types of electrodiagnostic nerve tests:
- Electromyography (EMG)
- Nerve conduction studies (NCS)
An electromyography (EMG) records and analyzes the electrical activity in muscles resulting from nerve stimulation. Electrical activity is an accurate measure of muscle activity, since problems with nerve activity will cause abnormal electric currents, resulting in abnormal muscle function. During an EMG, small, thin needles are placed in the muscle to record the electrical activity. You will be asked to relax the muscle and to tense it slightly so that the electrical signals can be observed and recorded.
Nerve Conduction Studies
Nerve conduction studies are often done along with an EMG to determine if a nerve is functioning normally. Wires (electrodes) are taped to the skin in various places along the nerve pathway, then the nerve is stimulated with an electric current. As the current travels down the nerve pathway, the electrodes placed along the way capture the signal and time how fast the signal is traveling. In healthy nerves, electrical signals can travel at up to 120 miles per hour. If the nerve is damaged, however, the signal will be slower and weaker. By stimulating the nerve at various places, your orthopedist can determine the specific site of the injury. Nerve conduction studies also may be used during treatment to test if progress is being made.
The following conditions benefit from electrodiagnostic nerve testing
- Carpal tunnel syndrome
- Cervical radiculopathy
- Diseases of muscle nerve roots, such as myasthenia gravis
- Disorders of motor neurons, such as sclerosis or polio
- Disorders in nerve roots, such as a herniated discs
- Inflammation of muscles
- Muscular disorders, such as muscular dystrophy
- Peripheral nerve damage (arms and legs)
- Peripheral nerve disorders, such as carpal tunnel syndrome
- Pinched nerves (radiculopathy) or nerve compression
- Thoracic outlet syndrome
- Ulnar nerve entrapment
Electrodiagnostic testing also can be used to determine the extent of injury to a nerve after an accident and to study the effects of diseases such as diabetes.